In a large wok or skillet heat 2 teaspoons oil until very hot but not smoking. Add carrots and celery; stir fry with wooden spatulas for 3 minutes. Add zucchini and onions. Cover pan, lower heat to medium-high, cook 1 minute. Uncover, stir a little, cover and cook 1 1/2 minutes more. Remove from heat.

In small saucepan pour in chicken broth. Sprinkle in arrowroot powder and about 1/8 teaspoon each garlic and ginger. With wire whisk, stir to dissolve. Thicken over medium heat. When slightly thick, add the cubed tofu. Stir gently to continue thickening and heating through the tofu. Combine with the vegetables. Serve over chow mein noodles and cooked brown rice.

Note: If pan isn't large enough, stir fry half the vegetables at a time in 1 teaspoon oil.